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UNIRAS Brief - 557/04 - iDEFENSE Security Advisory 10.07.04 RealNetworks Helix Server Content-Length Denial of Service Vulnerability


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   UNIRAS (UK Govt CERT) Briefing Notice - 557/04 dated 08.10.04  Time: 15:50 
  UNIRAS is part of NISCC (National Infrastructure Security Co-ordination Centre)
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  UNIRAS material is also available from its website at www.uniras.gov.uk and
         Information about NISCC is available from www.niscc.gov.uk
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iDEFENSE Security Advisory 10.07.04  RealNetworks Helix Server Content-Length Denial of
Service Vulnerability.


Remote exploitation of a denial of service (DoS) vulnerability in RealNetworks, Inc.'s 
Helix Server could allow an attacker to restart and potentially disable the server.

           ESB-2004.0633 -- iDEFENSE Security Advisory 10.07.04  RealNetworks Helix Server
                       Content-Length Denial of Service Vulnerability
                              8 October 2004

Product:                RealNetworks Helix Universal Server version 9
                        RealNetworks Helix Universal Mobile Server & Gateway version 10
Publisher:              iDEFENSE
Operating System:       Linux variants
Impact:                 Denial of Service
Access:                 Remote/Unauthenticated
CVE Names:              CAN-2004-0774
Original Bulletin URL:  http://www.idefense.com/application/poi/display?id=151

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RealNetworks Helix Server Content-Length Denial of Service Vulnerability

iDEFENSE Security Advisory 10.07.04: www.idefense.com/application/poi/display?id=151&type=vulnerabilities
October 7, 2004


RealNetworks Helix Universal Server is a universal digital media delivery platform with industry leading performance, integrated content distribution and Web services support. More information is available at http://www.realnetworks.com.


Remote exploitation of a denial of service (DoS) vulnerability in RealNetworks, Inc.'s Helix Server could allow an attacker to restart and potentially disable the server.

The problem specifically exists in the handling of specially crafted POST requests. Generating a request with the Content-Length header set to -1 triggers an integer handling error resulting in mass utilization of memory and CPU time.


Any unauthenticated remote attacker can exploit this vulnerability, which causes the affected system to utilize mass amounts of memory and CPU time. The system will no longer be able to process future requests.

The affected server must be restarted in order to resume normal functionality.


iDEFENSE has confirmed the existence of this vulnerability in RealNetworks Helix Server version 9.0.2 for Linux and version 9.0.3 for Windows. It is suspected that earlier versions on both platforms are vulnerable as well.


Usage of an inline application level filter can help mitigate risk of exploitation by scanning for and filtering invalid Content-Length parameters.


"Customers are encouraged to upgrade their Server software to the latest version, which contains a security patch."

RealNetworks has released binaries that guard against the described vulnerability. The related advisory from RealNetworks is available at:



The Common Vulnerabilities and Exposures (CVE) project has assigned the name CAN-2004-0774 to this issue. This is a candidate for inclusion in the CVE list (http://cve.mitre.org), which standardizes names for security problems.


07/01/2004   Initial vendor notification
07/01/2004   iDEFENSE clients notified
08/05/2004   Initial vendor response
10/07/2004   Coordinated public Disclosure


The discoverer of this vulnerability wishes to remain anonymous.

Get paid for vulnerability research http://www.idefense.com/poi/teams/vcp.jsp


Copyright (c) 2004 iDEFENSE, Inc.

Permission is granted for the redistribution of this alert electronically. It may not be edited in any way without the express written consent of iDEFENSE. If you wish to reprint the whole or any part of this alert in any other medium other than electronically, please email customerservice@xxxxxxxxxxxx for permission.

Disclaimer: The information in the advisory is believed to be accurate at the time of publishing based on currently available information. Use of the information constitutes acceptance for use in an AS IS condition. There are no warranties with regard to this information. Neither the author nor the publisher accepts any liability for any direct, indirect, or consequential loss or damage arising from use of, or reliance on, this information.

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UNIRAS wishes to acknowledge the contributions of iDEFENSE for the information 
contained in this Briefing. 
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